st: change values in the x-axis

Hello,
I am doing a bar graph and my x-axis takes values from -20000 to
20000. Is there a way to hide the negative signs of the values left of
the zero. e.g.
clear all
sysuse auto
gen price2=-price
gen n=_n
twoway (bar price n, horizontal) (bar price2 n, horizontal)
In the above graph i d like the values of the x-axis to be (left to
right): 20000 10000 0 10000 20000. Unfortunately I have quite a few
values and manually defining new label for my price2 would be hard.
Any suggestions would be much appreciated.
Regards
Manos
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